Session 44 -- The Status of Large Telescope Projects, Instrumentation and Plans for Large Science Projectects in the Areas of Wide-Field Surveys

Oral presentation, Wednesday, June 14, 1995, 2:00pm - 5:30pm

[44.04] The 3.5 Meter at Apache Point Observatory

Donald G. York (University of Chicago)

As of November 1, 1994, the 3.5 meter telescope at Apache Point is in regular science
operation. About 15\% of the time is still used for engineering. The performance is
still being improved. At present, we achieve 4 arc second rms absolute pointing from
20 to 89 degrees above the horizon. Image sizes are one arc second on a regular basis.
The best open loop tracking achieved is 0.1 arc sec. errors over 10 minutes, though it
can be worse. Closed loop tracking is better than 0.1 arc seconds. No aberrations
from the mirror supports have been detected. The honeycomb primary mirror is kept at
ambient temperature during the night time. Temperature non-uniformities in the back
and front plates are controlled to be the same to 0.1 degrees centigrade.

The telescope is regularly used with an infrared imager, a medium
resolution spectrograph, and a large format, drift scan CCD camera. An
echelle spectrograph, a high angular resolution camera, and an adaptive
optics system are being integrated into the system. Instrument changes can
be made in less than 20 minutes, at night. All instruments are operational
and can be mounted by one person at any time. The observatory is operated
by a full time staff of 6.6 individuals.

Remote operations are possible from all ARC campuses. Over 70\% of the
observing is carried out this way, with site visits by astronomers only for
mounting visitor instruments or for training purposes. Observing functions,
including complete telescope control, instrument control, and data
retrieval are carried out by the remote observer. The telescope is
scheduled on an hourly basis, two months in advance of the actual runs. The
individual university members of the project control their own time
allocations and intra-institutional trades of time. The project partners
are the University of Chicago, New Mexico State University, Princeton
University, the University of Washington, and Washington State University.